Vehicle transmissions, specifically planetary gear automatic power transmissions, typically have a park brake mechanism to resist the vehicle's natural tendency to roll down a sloped surface when the vehicle is in park. The contents of such a park brake generally include some sort of gear that is fixed with respect to the output shaft of the transmission and a pawl designed to selectively engage with the gear when the park brake is activated. The pawl substantially prevents the output shaft and attached gear from rotating when the pawl engages with the recesses between the gear teeth. One example of a successful park pawl arrangement is described in commonly assigned U.S. Pat. No. 5,630,339 entitled “Park Mechanism for Vehicle Transmission,” Tuday, T May 20, 1997, and hereby incorporated by reference in its entirety.
Vehicles with complex non-traditional powertrains, like electro-mechanical vehicles, still require a park brake mechanism. However, the alteration of some components of the transmission may require the park pawl and its complementary components to be altered as well. For example, some hybrid electro-mechanical transmissions require the use of two electric motors to supply power to the output shaft of the transmission. The two motors significantly increase the amount of packaging space needed for the transmission. Therefore, the surrounding transmission components, including the park brake mechanism, must be adjusted to accommodate the additional power supply. The location and placement of these surrounding components, however, is limited by the dimensions of neighboring vehicle components and by any clearance requirements for the underbody of the vehicle. The park pawl for the aforementioned transmission was placed farther rearward to accommodate the second electric motor. A cover or housing was required to protect the park brake from contamination. Major design considerations of the rear cover include manufacturability, structural integrity, weight, and material costs requirements.